Method for making dry reed switches

ABSTRACT

A dry reed switch is provided with a metal tube penetrating into one of the ends of the switch envelope and carrying at its end a small glass tube. The free end of this latter tube is susceptible of melting under the action of infrared rays so as to close the envelope of the switch after evacuation thereof.

July 31, 1973 M. Nmoms @ML METHOD FOR MAKING DRY REED SWITCHES Original Filed July 7, 1970 O S if F.

United States Patent O U.S. Cl. 65-34 1 Claim ABSTRACT OF THE DISCLOSURE A dry reed switch is provided with a metal tube penetrating into one of the ends of the switch envelope and carrying at its end a small glass tube. The free end of this latter tube is susceptible of melting under the action of infrared rays so as to close the envelope of the switch after evacuation thereof.

This is a continuation of application Ser. No. 52,836 tiled July 7, 1970, now abandoned.

The present invention relates to dry reed switches, As is well known such switches comprise within an evacuated, generally elongated, enclosure, two blades or reeds arranged for contacting each other under the action of an externally operated magnetic iield.

For various reasons the evacuating of such enclosures has always been quite a problem. This evacuation is generally performed by means of an external exhaust tip which projects towards outside. The external surface of the enclosure is therefore no longer even and smooth and this may complicate the positioning of the enclosure within the coil generating the magnetic lield. On the other hand, it is difficult to position the exhaust tip at one of the ends of the enclosure since dry reed switches have extremely small sections.

It is an object of the invention to avoid such difficulties.

According to the invention there is provided a dry reed switch comprising: an elongated envelope; within said envelope two reed switch contact elements capable of making contact with each other under the action of an external magnetic field; a metal tube extending into said envelope at one end thereof, said metal tube carrying at its end within said envelope a glass tube, tightly connected thereto and having a free end portion, at least said end portion of said glass tube being capable of absorbing infrared rays, at least that part of said envelope which surrounds said infrared ray absorbing tube portion being transparent to said rays.

According to the invention there is provided an enclosure comprising a wall having a pumping tip integrally incorporated therein and extending into said enclosure, said tip having an end susceptible of being closed off by melting under the action of infra-red rays.

The invention provides a general method of closing ott a pumping or an exhaust tip of an envelope which, as the case may be, has been lled with a gas or evacuated. At least the end of the tip is made of glass and is placed within the envelope and before the latter is disconnected from the pumping `system is closed by melting it under the action of infra-red rays. Of course the glass must be such as to be capable of melting under the action of infrared rays. To this end colour glass must be used, for example a glass whose constituent oxydes have been at least partially and locally reduced. Also, at least a portion of the envelope concerned must be transparent to infra-red rays so that the latter may reach the tip without affecting the envelope.

ICC

For a better understanding of the invention and to show how the same may be carried into effect reference will be made to the drawing accompanying the following description and in which:

FIGS. 1 and 2 are sectional views of two embodiments of the invention;

FIGS. 3 and 4 are similar views, on a larger scale, showing a detail;

FIG. 5 shows a dry reed switch in the process of the evacuation thereof;

FIG. 6 shows a terminated dry reed switch.

The envelope 1 of glass or metal, a portion of which is shown in FIG. 1, has an extension in the form of a cylindrical solid of revolution 3 made of a material transparent to infra-red radiation. This cylindrical portion comprises inside it a connector or exhaust tip 4 which is made of a glass compatible with the material of the cylinder 3. The cylindrical part 3 may be connected, for the purpose of creating a vacuum within the envelope 1, to an exhaust piping 5 through the medium of a rubber connector 6. In order to reduce the losses as far as possible, the tip 4 is made as short as possible and has an adequate diameter. Its end inside the cylindrical part 3 will previously have been drawn to facilitate the closing otf of its orifice by local melting of the glass under the action of infra-red rays, schematically illustrated by the arrow IR.

Another advantage of the invention consists in the fact, when a filling is made by means of a gas or a vapour with a pressure above the atmospheric pressure, that both the internal and external walls of the tube 9 are submitted to the same pressure.

For the melting process, according to the specification given below, no particular precautions are needed such as those which are imperative with a conventional tip, the enclosure internal overpressure, as related to the external atmospheric pressure, being a too important stress applied to the glass in a melted state to be supported by this conventional tip.

In the embodiment shown in FIG. 2, the cylindrical extension 3 of the enclosure is closed otf by a conventional flat bottom. Lead throughs 7 have been also shown. The exhaust tip 4 is in the form of a metal tube 8 of appropriate coefficient of expansion, at the internal end of which tube a tapered glass tip 9 has been bonded, this tip being designed to behave in the same way as described in the case of FIG. l. As in FIG. l, the tip 4 has a tapered extremity and is of such a nature that it can be melted and closed ott under the action of infra-red rays. For example it has been darkened by reduction of the oxides contained in the glass. In both cases the tip or its glass extension if the former is of metal, can be made of coloured glass which absorbs infra-red radiation.

As shown in FIG. 3 and 4, the operations of connecting the metal tube 8 to the glass base of the envelope, and of connecting the glass tube 9 to the metal tube 8, can be carried out simultaneously. FIG. 3 illustrates how these elements are assembled at the levels which they are ultimately to occupy in relation to one another. They are of course appropriately supported by some suitable means (not shown in order not to overburden the drawing). The local melting of the glass parts of said elements is carried out, for example by heating by means of a ring of gas burners, as schematically illustrated by the arrows f, in order to effect the simultaneous connection of said three elements. The finished condition is illustrated in FIG. 4.

FIG. 5 shows a reed-type contact-breaker with two flexible reeds 11 and 12 bonded at the ends 13 and 14 of a transparent glass tube 15. A metal exhaust tube 8 extends into the envelope at one of the ends of the envelope. The metal tube is prolonged at its inner end by a glass tube 9 of substantially the same diameter, the body of which is coloured or the extremity of which has been coloured, for example by reduction of its constituent oxides, so as to make it possible to melt it under the action of infra-red rays. The evacuation of the tube 15 takes place through the exhaust piping 5 mounted by means of a rubber connector 6. The procedure is in itself quite conventional.

The same reed-type switch is shown in FIG. 6 after the closing o of the extremity 16 of the tip 9 by melting by infra-red rays, schematically illustrated in FIG. 5 by the arrow IR. The switch is then ready for use after the vaporisable annular getter 17, designed to absorb the residual gases or those liable t0 be liberated during the course of operation of the contact-breaker, has been vaporized, thus forming on the internal wall of the tube the well-known shiny coating 13 Which is capable of fixing gas molecules. The getter is carried by the two branches 19a and 19h 0f a wire 19 which is soldered to the reed 11 prior to the bonding of said reed to the glass tube 15 at the end 13.

It may thus be seen that no exhaust tip in the usual sense of the word has been used, since the metal tip 8 need not be closed off externally. Also the body of the envelope 8 remains externally smooth. Thus, any trouble, so far caused by the evacuation of minute dry reed switch, has been avoided.

What is claimed is:

1. A method of making a dry reed switch comprising providing an elongated envelope containing two reed switch contact elements capable of making Contact with each other under the action of an external magnetic field,

providing a metal tube extending into said envelope at one end thereof and having a portion external to said envelope,

tightly connecting a glass tube to said metal tube as a continuation thereof with the glass tube extending into the envelope and having at least the free end portion made of colored glass capable of absorbing infrared rays, i

at least that part of said envelope which surrounds said infrared ray absorbing tube portion being transparent to infrared rays,

using said metal and glass tube for the passage of air or other gas to cause the internal pressure in the envelope to differ from ambient atmospheric pressure,

passing infrared rays through the envelope from an external source to impinge on at least the free end portion of the tube made of colored glass,

said infrared rays passing through said envelope Without substantial absorption, and

said infrared rays being absorbed by said colored glass causing said colored glass to melt and close olf the free end portion of said glass tube to seal the envelope.

References Cited UNITED STATES PATENTS 2,533,512 12/1950 Samuel 220-2.3 R 3,217,088 11/1965 Steireman 65--40VX 3,242,557 3/ 1966 Ellwood 65-DIG. l2

FOREIGN PATENTS 111,419 8/1940 Australia.

ROBERT L. LINDSAY, I R., Primary Examiner U.S. Cl. X.R. 

